A. A labeled, soluble, native glycoprotein (GP) or possibly glycosaminoglycan (GAG) was isolated from the medium after incubation of corneas with labeled precursors; its synthesis was stimulated 4-5 fold by added retinol when incubating corneas from vitamin A-deficient rats, and was decreased 3-4 fold when comparing deficient to normal corneas. The origin of this GP or GAG in corneal epithelium and its possible transfer to stroma will be investigated. Its chemical nature and properties will be determined, including sugar composition and possible sulfate content. The mechanism of the stimulation of its synthesis will be studied by determining whether prior protein synthesis is needed to obtain vit. A-stimulation. Since it is our hypothesis that vit. A affects sugar addition in GP synthesis, we will investigate corneal epithelial glycosyltransferases for vit. A stimulation, using cell-free systems, sugar nucleotides and endogenous or, if possible, exogenous sugar acceptors. Sugar-lipid intermediates will be isolated from corneas to test the hypothesis that retinylglycosyl phosphates are intermediates in corneal GP or GAG synthesis. They will be tested as possible sugar donors. Cross-over experiments will be done to determine if defective GP or GAG synthesis in deficient corneas' subcellular systems can be corrected by addition of glycosyltransferases and/or retinylglycosyl phosphate(s) from normal corneas. B. Attempts will be made to explain "corneal melting" (sudden dissolution of corneal stroma in severe vit. A deficiency). (a) Long-term timed radioautography will be undertaken to follow a labeled pulse of glucosamine from epithelium possibly into stroma with progressive vit. A deficiency, to determine if "melting" is caused by lack of synthesis of a stromal component. (b) We found a serum alpha-macroglobulin with antiprotease activity depressed in vit. A deficiency. We will test the hypothesis that this GP has collagenase-inhibitory activity; that it is present in lachrymal fluid bathing the cornea; that it declines severely in severe vit. A deficiency and then releases collagenase activity and causes "corneal melting".